A gear drive device is known that enables improved workability of the positioning operation when the device is required to be installed with a meshing position of a second gear with a first gear at a predetermined phase (see for example Patent Document 1).
The gear drive device described in Patent Document 1 includes jigs extending beside and parallel to a first shaft and a second shaft of a back case. Inserting the jigs through positioning holes and the like and installing (supporting) the gears in order on the first shaft and the second shaft allows the rotational positions (phase, mesh position) of the gears to be fixed with respect to the back case. In other words, the jigs can be inserted at the same time as the first shaft and the second shaft are inserted through the gears, which makes it possible to perform installation and positioning operations at the same time, allowing workability to be improved.